1. Field of the Invention
The present invention relates to a valve slide with a slide housing. The slide has a passage opening which can be closed by means of a closing member which is slidable in its plane. A sealing surface is provided in the region of the slide passage opening. In the closed position of the closing member, a circumferentially closed sealing member arranged on the closing member rests against the sealing surface. Each imaginary straight generatrix of the sealing surface extends parallel to the axis of the slide passage opening. The circumferentially closed sealing member which is formed of one piece has sections of different length and/or shapes which are located in different planes. Two principal sections of the sealing member are located in planes which extend perpendicularly to the axis of the slide passage opening. The two principal sections are spaced apart from each other and are connected by lateral sections. The closing member has a surface which carries the circumferentially closed sealing member and corresponds in its shape to the sealing surface of the housing.
2. Description of the Prior Art
A valve slide of the above-described type is known. The housing of this valve slide is made in one piece of gray cast iron and has rough sealing surfaces and is structurally very simple. The closing member, which may also be made in one piece, has a large volume and is made of a rubber-elastic material which, because of its large elastic volume, can compensate the above-described roughness of the unfinished sealing surface of the one-piece housing. Valve slides of this type are used in water supply mains. This type of valve slide is completely unsuitable in situations where high-quality seals are necessary and required as in, for example, vacuum and high-vacuum systems because the required degree of tightness cannot be achieved with valve slides of this type.
In a valve slide of a similar type disclosed in German Auslegeschrift No. 12 23 212, the sealing member is pressed with a U-shaped lower portion in the lower region of the slide plate against the inner side of the flow duct and with a stirrup-shaped upper portion in the upper region of the slide plate against the outer wall of the flow ducts. The sealing member is mounted in grooves in the housing. In addition, the sides of the U-shaped lower portion of the sealing member rest with the ends thereof against projections attached to the housing and, moreover, the U-shaped lower portion of the sealing member is reinforced by a resilient insert. The sealing member is made of one piece. The upper portion and the lower portion are connected through webs which extend parallel to the axis of the passage opening. When the valve slide is actuated, the slide plate slides transversely along these webs which rest against surfaces which are inclined obliquely relative to the direction of movement of the slide plate. Accordingly, there is the danger that the surfaces of the sealing member are damaged in the region of these webs, so that a valve slide of this specific construction is not suitable for vacuum systems and high-vacuum systems.
Slides for the use in vacuum and high-vacuum systems have been developed. The closing members of these slides for these systems requiring high-quality seals are always constructed in several parts. The closed members have a sealing plate with an annular seal which is arranged on the sealing plate and is located in a plane. A sealing surface on the housing receiving this plane annular seal extends perpendicularly to the axis of the slide passage opening. A spreading device is connected to the sealing plate which carries the sealing ring.
As disclosed in Swiss Pat. No. 659,512 and U.S. Pat. No. 4,560,141 tiltable block-type members have been developed for these spreading devices. The tilting motion of the block-type member effects the axial displacement of the structural components of the closing member, so that the sealing member is placed and pressed against the sealing surface. Rolling members have also been used in such spreading devices. The rolling members run onto inclined tracks so as to achieve the above-mentioned axial displacement of the structural components supporting and guiding the rolling bodies, as disclosed in German Pat. No. 32 09 217, German Offenlegungsschrift Nos. 24 04 944, 25 28 043, U.S. Pat. Nos. 3,185,435 and 4,291,861. The prior art also includes spreading devices with swingable lever systems which usually cooperate with springs, as described in German Auslegeschrift No. 25 23 152, U.S. Pat. Nos. 3,216,694, 2,850,260 and 3,262,672. Also, closing members have been proposed which are operationally connected to chambers to which a pressure can be admitted, so that the closing member moves into the slide passage opening or the sealing ring supported by the closing member and the sealing plate rest against the sealing surface of the housing.
It is apparent that the closing member constructions of the above-described valve slides used for high quality seals are extremely complicated and cumbersome. Also, it should be noted that these parts which form the entire closing member move relative to each other during operation and sometimes extremely high forces act on these parts. In addition, the parts which move relative to each other cannot and may not be lubricated because the vacuum would otherwise be impaired.
The above-described complicated constructions have the additional disadvantage that a closing member having many parts cannot be used in quick-closing valves and emergency valves because, under the influence of high accelerating forces as they are unavoidable in quick-closing valves and emergency valves, the spreading mechanism begins already to operate to inertness before the closing member has been moved into its closing position, so that the closing member is wedged into the housing portion in which it is received before it reaches the closing position.
It is, therefore, the primary object of the present invention to further develop a valve slide of the above-described type, so that it can be used in vacuum systems and high-vacuum systems in which high-quality seals are needed. In order to meet these requirements, the reproducible conditions in the various closing procedures must be provided for all portions of the circumferentially extending sealing member. In addition, during closing of the sealing member and when the closing pressure is applied, the load should be applied on the sealing member only essentially transversely of its longitudinal direction, so that transverse forces on the sealing member are avoided. Moreover, it must be possible to finish the sealing surfaces in order to meet the sealing requirements. Also, the closing member proper should have few parts which are movable relative to each other, so that the closing member can also be used in quick-closing and emergency valves where high accelerations occur.